In the field of nasal spray devices of the one-dose or two-dose type, ergonomic and operating constraints and needs exist that are different from those that exist in multi-dose systems. In particular, this is due to the small size of the devices, which can give rise to handling difficulties. In addition, when the dispenser device is a two-dose device, the dose must be subdivided into two half-doses to be dispensed successively, one in each nostril. It is then essential to guarantee that the dose is subdivided safely and reliably.
Furthermore, one-dose or two-dose devices are often used to dispense medication that is designed to be taken once only, such as vaccines or medication to be taken in an emergency, and sometimes such devices are not designed for self-administration by the patient, but rather they are designed to be dispensed to the patient by another person. That makes it absolutely necessary for the nasal device to be positioned correctly in the nostril, and for it to be simple, safe, and reliable to operate.
Currently, no fully satisfactory solution has been proposed for simultaneously solving those safety and reliability problems. In order to subdivide the dose into two half-doses in a two-dose device for dispensing separately into each of the two nostrils, existing devices are generally made up of two elements, one of which supports the reservoir, the other element supporting the piston. When they are compressed axially towards each other, the first half-dose is delivered through the dispensing orifice into the nostril. In order to subdivide the dose, the stroke of the piston is stopped half-way along its length by a shoulder, and in order for the piston to travel over the second portion of its stroke, i.e. in order to dispense the second half-dose, it is necessary to turn the piston element manually relative to the reservoir. That type of system is safe and accurate, but it requires relatively complex handling, and thus both hands to be used in order to obtain the desired result and to be capable of dispensing the two half-doses successively in respectively ones of the two nostrils.
Other types of solution also include an abutment formed by a shoulder and turning, but turning is performed automatically by the system, e.g. by means of a resilient component such as a spring, as soon as the piston ceases to be pressed, after the first half-dose has been dispensed. That system is relatively simple to operate but it is not completely safe because the piston ceasing to be pressed can occur unintentionally, e.g. due to shaky hands, to indecisiveness, to fear of the spray entering the nose, etc. The result is that the two half-doses might be dispensed into the same nostril.
Concerning the ergonomic problem due to the small size of the device, existing devices propose no solution. Such devices need to be pressed axially towards the nostril, and that is relatively difficult to achieve because of the relatively small size of that type of device, the difficulty being even greater when the administration is performed by another person. The axial pressing required to actuate the device can cause the device to move into the nostril and give rise to injury, and even a risk of the dose being dispensed poorly because of a reaction by the patient, e.g. the patient recoiling suddenly as the dispensing is taking place. An object is thus to obtain a dispensing orifice which remains stationary throughout the dispensing of the dose into the nostril, which can be particularly important, in particular with medication to be taken once only, such as vaccines, for which inaccurate metering of the dose cannot be corrected by a second administration.
Document U.S. Pat. No. 5,570,821 discloses a semi-liquid fluid dispenser having a ratchet column associated with a piston, said ratchet column being displaced vertically by means of a lateral actuating button.